Smoothed particle hydrodynamics simulations of counterrotating disk formation in spiral galaxies

摘要

We present the results of smoothed particle hydrodynamics(SPH) simulations of the formation of a massive counterrotating disk in a spiral galaxy. The current study revisits and extend (with SPH) pre- vious work carried out with sticky particle gas dynamics, in which adiabatic gas infall and a retrograde gas-rich dwarf merger were tested as the two most likely processes for producing such a counterrortating disk. we report on experiments with a cold primary similar to our Galaxy, as well as a hot, compact primary modeled after NGC 4138. We have also conducted numerical experiments with varying amounts of prograde gas in the primary disk and an alternative infall model(a spherical shell with retrograde angular momentum).